\input pstfig
$
\setcoorunit{3}{1}
\psset{yunit=0.4\psxunit}
\drawaxes{-2.6}{5}{-3}{3.2}
\markxlabel{-1.5}{-\frac{3}{2}\pi}{-1.5em}
\markxlabel{-0.5}{-\frac{\pi}{2}}{1ex}
\uput{0.3ex}[-50](0,0){\scriptstyle O}
\markxlabel{0.5}{\frac{\pi}{2}}{-1ex}
\markxlabel{1.5}{\frac{3}{2}\pi}{1em}
\markxlabel{2.5}{\frac{5}{2}\pi}{-1ex}
\markxlabel{3.5}{\frac{7}{2}\pi}{1em}
\psplot{-2.5}{4}{cos(x*\pinum)}
$
\bye
